smarty_preprocess doesn't get hooked in Drupal6

Hi, since "_smarty_variables" is depricated in Drupal 6 I tried the
new preprocess function in my template.php shown up in

-> http://drupal.org/node/223430

But At all I didn't find a way to get the preprocess function
hooked.

Somebody out there who get this worked?
I strongly need to setup own vars :(

thx!!
marco